Pickup unit homing mechanism for a disk drive unit

ABSTRACT

A disk drive unit for a disk includes a mounting plate, a spindle motor assembly, a slide mechanism provided with a slide, a pickup unit mounted on the slide, a first transmission member operatively connected with the slide, and a second transmission member. The first transmission member is positioned such that it is in engagement with the second transmission member when the pickup unit is in its read and/or write position, and such that the first transmission member is out of engagement with the second transmission member when the pickup unit is in its home position. In order to bring the first and second transmission members into engagement, the transmission members are provided with engagement members. As a result, a limit switch assembly is no longer necessary.

The invention relates to a disk drive unit for a disk.

Disk drive units of this type are known in many embodiments thereof, andgenerally comprise a mounting plate, a spindle motor assembly, a pickupunit for reading and/or writing data on the disk, and a slide mechanismwhich is adapted to move the pickup unit along the surface of the diskbetween a home position and a read and/or write position. In general theslide is moved by a transmission assembly comprising a gear rackoperatively coupled with the slide and in engagement with a gear wheelwhich is driven by a DC motor. In order to detect the home position ofthe pickup unit, disk drive units of this type generally comprise anadditional limit switch which is adapted to stop the DC motor when thehome position is reached. However, the use of a limit switch within adisk drive unit leads to additional assembly and material costs, whichcomprise in general the costs for a switch, some resistors andconnectors, an I/O port and additional space on the circuit board.

It is an object of the invention to provide a disk drive unit for a diskwherein the above-mentioned additional limit switch is not needed.

In order to accomplish that objective, the disk drive unit according tothe invention comprises a pickup unit mounted to a slide of a slidemechanism, which slide mechanism is adapted to move the pickup unitalong the disk between a home position and a read and/or write position,the slide mechanism comprising a driven first transmission member whichis operatively connected to the slide for moving slide, and a drivingsecond transmission member which is only in engagement with the firsttransmission member when the pickup unit is in the read and/or writeposition, and wherein the pickup unit and the second transmission membercomprise engagement members which are adapted to come into engagement atleast when the second transmission member is not in engagement with thefirst transmission member so as to move the pickup unit away from thehome position, which movement causes the first and second transmissionmembers to engage.

In the disk drive unit according to the invention, the first and thesecond transmission member are disengaged when the pickup unit reachesits home position, whereby the movement of the pickup unit is stopped.In other words, the transmission assembly of the disk drive unit isadapted to stop the movement of the slide when the pickup unit reachesits home position, so that a limit switch is no longer necessary fordetecting the home position of the pickup unit, which is cost-effective.In order to bring the first and the second transmission member back intoengagement, the invention provides engagement members at the secondtransmission member and the pickup unit.

Further features have the advantage that the engagement members of thepickup unit and the second transmission member do not interfere with themovement of the pickup unit when it is moved to its home position.

A cam is also provided which has the advantage that the cam is a verysimple and low-cost means for initiating the engagement of theengagement members of the pickup unit and the second transmissionmember. Moreover, as a movable bearing plate coupled to the actuator ofthe pickup unit is generally used in disk drive units, the addition ofthe cam is the only change to be made to the bearing plate in order toobtain the disk drive unit according to the invention, which iscost-effective.

Other features have the advantage that a gear rack and a gear wheelhaving a protrusion are simple to manufacture.

Further features have the advantage that the movement of the pickup unitaway from its home position is controlled by a control unit which isalready present within the disk drive unit.

Other features have the advantage that the engagement of the first andthe second transmission member is detected by the detection of thesurface of the disk, so that no additional detecting members arenecessary for detecting the engagement of the transmission members,which is cost-effective.

The invention also relates to a device for reading and/or writinginformation, such as data, from/on an optical disk. The device accordingto the invention is provided with the disk drive unit according to theinvention.

These and other aspects and advantages of the invention will be apparentfrom the following description with reference to the drawings.

FIG. 1 is a perspective top view of a preferred embodiment of the diskdrive unit according to the invention.

FIG. 2 is a perspective bottom view of the disk drive unit of FIG. 1;

FIG. 3 is a perspective view of the first transmission member of thedisk drive unit as shown in FIG. 2, on a larger scale; and

FIG. 4 is a perspective view of the second transmission member of thedisk drive unit as shown in FIG. 2, on a larger scale.

The drawings show a preferred embodiment of the disk drive unitaccording to the invention. This disk drive unit 1 may be used in adevice for reading and/or writing data on a disk, such as a compact diskplayer, which is adapted to read and/or write compact disks for audioand/or video by means of an optical or magnetic reading and/or writingmember.

With reference to FIGS. 1 and 2, the preferred embodiment of the diskdrive unit comprises a mounting plate 2 and a spindle motor assembly 3on the mounting plate which is adapted to support and to rotate a diskwhen positioned on the spindle motor assembly 3. In order to read and/orwrite the data on the disk, a pickup unit 4 is provided which comprisesa laser assembly 5. In operation, the disk is rotated and the laserassembly 5 is translated along the disk in a radial direction withrespect to the disk. The focusing of the laser assembly 5 in aperpendicular direction with respect to the disk is performed by a focusactuator mechanism within the laser assembly (not shown). The movementof the laser assembly in a radial direction along and with respect tothe disk is performed by a slide mechanism 6 which roughly positions thepickup unit with respect to the disk and by a positioning mechanism 7 ofthe pickup unit 4 which performs the fine positioning of the laserassembly 5.

With reference to FIG. 2, the slide mechanism 6 of the preferredembodiment of the disk drive unit 1 comprises a slide 8, and the pickupunit 4 is mounted on the slide 8. The positioning mechanism 7 of thepickup unit 4 comprises a bearing plate 9 which is pivotably mounted tothe slide 8 by means of a pivot pin 10. The positioning mechanism 7further comprises an actuator 11 which is operatively connected to thebearing plate 9 and the slide 8. The actuator 11 is adapted to rotatethe bearing plate 9 around the pivot pin 10 with respect to the slide 8.The laser assembly 5 is mounted to the bearing plate 9 at a distancefrom the pivot pin 10 such that the laser assembly 5 is slightly movedalong the disk due to the rotation of the bearing plate 9.

The slide mechanism 6 of the preferred embodiment of the disk drive unit1 is adapted to move the pickup unit 4 to a home position, which is nearthe spindle motor assembly 3 as shown in FIGS. 1 and 2, and an operatingposition where the laser assembly 5 of the pickup unit 4 is enabled toread and/or write the data on the disk. The home position of the pickupunit 4 is the starting point from which a read and/or write sequence ofthe disk is initiated.

With reference to FIG. 2, the slide mechanism 6 comprises a first and asecond transmission member, wherein the first transmission member is agear rack 12 mounted to the slide 8 and the second transmission memberis a gear wheel 13 rotatably mounted to the mounting plate 2. The gearrack 12 is adapted to come into engagement with the gear wheel 13. Whenthe gear wheel 13 and the gear rack 12 are engaged, the rotation of thegear wheel 13 leads to a displacement of the slide 8. As shown in FIG.2, the preferred embodiment of the disk drive unit 1 comprises a DCmotor 14 which is adapted to rotate the gear wheel 13 by means of aseries of gearwheels 15.

The gear rack 12 of the preferred embodiment of the disk drive unit 1 isshown in more detail in FIG. 3. As shown, the gear rack 12 is formed ona mounting member 16 in order to be mounted to the slide 8. The mountingmember 16 further comprises a freewheel section 17 provided at one endof the mounting member 16. The gear rack 12 is positioned at themounting member 16 such that the gear wheel 13 is in engagement with thegear rack 12 when the pickup unit is in its read and/or write position,and such that the gear wheel 13 is positioned at the freewheel section17 when the pickup unit 4 is in its home position. For the properfunctioning of the slide mechanism 6, the freewheel section 17 is notstrictly required and the part containing the freewheel section maytherefore be omitted so that the gear rack is just shorter. The slidemechanism 6 will work properly when the gear wheel 13 and the gear rack12 are disengaged with the pickup unit 4 in its home position due to thelimited length and the position of the gear rack 12 with respect to theslide 8 and the gear wheel 13.

As shown in FIG. 2, the bearing plate 9 of the pickup unit 4 of thepreferred embodiment of the disk drive unit 1 comprises a cam 18 as anengagement member. As the bearing plate 9 is rotatable due to the actionof the actuator 11 of the pickup unit 4, the cam 18 is movable due tothe action of the actuator 11 too.

As shown in FIGS. 2 and 4, the gear wheel 13 of the preferred embodimentof the disk drive unit 1 is provided with a protrusion 19 as anengagement member. The protrusion 19 is positioned such that it isenabled to come into engagement with the cam 18 of the pickup unit 4only when the actuator 11 has moved the cam 18 towards the gear wheel 13by rotating the bearing plate 9. As a result, the cam 18 and theprotrusion 19 do not interfere with the movements of the pickup unit 4when the pickup unit 4 is moved to its home position.

The preferred embodiment of the disk drive unit 1 further comprises acontrol unit (not shown) which is connected to the spindle motorassembly 3, to the laser assembly 5, to the actuator 11, and to the DCmotor 14 (by means of electrical conductors, not shown). The controlunit is adapted to power and control at least the above-mentionedelectrical members.

With reference to FIG. 2, the operation of the slide mechanism 6 of thepreferred embodiment of the disk drive unit is as follows:

After reading and/or writing of the data on the disk, the control unitapplies a constant voltage to the DC motor 14 of the slide mechanism 6during a fixed time period. The voltage is provided such that the gearwheel 13 is rotated in the direction indicated by arrow 20. As the gearrack 12 and the gear wheel 13 are in engagement, the pickup unit 4mounted on the slide 8 is translated towards its home position. When thehome position is reached, the gear rack 12 and the gear wheel 13 aredisengaged due to the limited length and the position of the gear rack12 with respect to the slide 8 and the gear wheel 13, whereby themovement of the pickup unit 4 is stopped and the gear wheel 13 isenabled to rotate freely about its axis at the position of the freewheelsection 17 on the mounting member 16. The fixed time period of thevoltage applied to the DC motor 14 of the slide mechanism 6 is based onthe time which is needed for moving the pickup unit 4 from its outermostposition towards its home position. As the gear rack 12 and the gearwheel 13 are disengaged when the pickup unit 4 reaches its homeposition, any remaining rotations of the gear wheel 13 in the case thepickup unit 4 has not been moved from its outermost position will nothave any impact on the slide mechanism 6.

A start-up procedure is initiated when the fixed time period has passedand a new read and/or write sequence is desired. This start-up procedureis necessary for bringing the gear rack 12 and the gear wheel 13 backinto engagement in order to enable the laser assembly 5 of the pickupunit 4 to read and/or write the data on the disk.

In the start-up procedure, the control unit powers the actuator 11 ofthe pickup unit 4 such that the cam 18 of the pickup unit 4 is broughtinto a position where it is enabled to come into engagement with theprotrusion 19 on the gear wheel 13.

In the start-up procedure, the control unit also causes a series ofvoltage pulses to be applied to the DC motor 14 of the slide mechanism 6such that the gear wheel 13 rotates stepwise in a direction opposite toarrow 20. The duration of each voltage pulse is such that the gear wheel13 performs approximately half a revolution per voltage pulse. Thus,when the gear wheel 13 is rotated, the protrusion 19 on the gear wheel13 will hit the cam 18 of the pickup unit 4 and as a result, the pickupunit 4 is moved away from its home position. This movement of the pickupunit 4 causes the gear rack 12 and the gear wheel 13 to come intoengagement.

During the start-up procedure, the control unit also starts focusing ofthe laser assembly 5. During focusing, which is also performed duringthe reading and/or writing of the data on the disk, the laser assembly 5is turned on in order to detect the information area of the disk. Aftereach voltage pulse applied to the DC motor 14 of the slide mechanism 6,the control unit determines whether the laser assembly 5 has detectedthe information area of the disk. When the information area of the diskis detected by the laser assembly 5 during the start-up procedure, thegear rack 12 and the gear wheel 13 must be properly engaged and thestart-up procedure is stopped. In general, the gear rack 12 and the gearwheel 13 will come into engagement within two or three half rotations ofthe gear wheel 13. In order to prevent a time consuming start-upprocedure when no disk is placed within the disk drive unit or when thelaser assembly 5 is unable to detect any information area on the disk,the sequence of applied voltage pulses is limited, preferably to sixpulses.

As is clear from the above description, the engagement of the gear rack12 and the gear wheel 13 is detected by the laser assembly 5 of thepickup unit 4, so that the pickup unit 4 is able to function as adetecting member, without the need for an additional component.

It should be understood from the above description that the movement ofthe pickup unit 4 is advantageously stopped at its home position due tothe limited length and the position of the gear rack 12 with respect tothe slide 8 and the gear wheel 13, and that the pickup unit 4 is movedaway from its home position by the cam 18 on the pickup unit 4 and theprotrusion 19 on the gear wheel 13 and by the action of the actuator 11of the pickup unit 4, during all of which the control unit powers andcontrols the rotation of the gear wheel 13 and the action of theactuator 11. As a result, a limit switch for the detection of the homeposition of the pickup unit 4 is not required, which leads to a savingin manufacturing cost of the disk drive unit 1.

As the gear rack 12, the gear wheel 13 provided with the protrusion 19,and the cam 18 provided on the pickup unit 4 are very simple tomanufacture, the manufacturing costs of these means are relatively low.

The invention is not restricted to the above examples as shown in thedrawing, which can be varied in several ways without departing from thescope of the invention.

For example, it should be understood that the engagement member of thepickup unit is not limited to a cam and that the engagement member ofthe second transmission member is not limited to a protrusion providedon the second transmission member. The engagement members may be anykind of cooperating members, such as brushes or the like, as long as thepickup unit is pushed away from its home position by the movement of thesecond transmission member.

As a further example it should be understood that the first and thesecond transmission member are not limited to a gear wheel and a gearrack. Any set of transmission members may be provided, such as a runningsurface driven by a wheel or gear wheels comprising free runningsections and operatively connected to the pickup unit in order to movethe pickup unit.

In general it is noted that, in this application, the expression“comprising” does not exclude other elements, and “a” or “an” does notexclude a plurality. A single processor or unit may fulfil the functionsof several elements in the appended claims. Reference signs in theclaims shall not be construed as limiting the scope thereof.

1. A disk drive unit for a disk comprising: a slide of a slidemechanism; a pickup unit mounted to the slide wherein the slidemechanism is adapted to move the pickup unit along the disk between ahome position and a read and/or write position, the slide mechanismcomprising: a driven first transmission member which is operativelyconnected to the slide for moving the slide; and a driving secondtransmission member which is only in engagement with the firsttransmission member when the pickup unit is in the read and/or writeposition, wherein the pickup unit and the second transmission membercomprise engagement members which are adapted to come into engagement atleast when the second transmission member is not in engagement with thefirst transmission member so as to cause movement of the pickup unitaway from the home position, wherein the movement causes the first andsecond transmission members to engage; wherein the engagement member ofthe pickup unit is operatively coupled to an actuator of the pickupunit, and wherein the engagement member of the pickup unit is adapted tocome into engagement with the engagement member of the secondtransmission member owing to action of the actuator of the pickup unit;wherein the engagement member of the pickup unit includes a cam at abearing plate of the pickup unit, wherein the bearing plate isoperatively coupled to the actuator of the pickup unit and is movableabout a pivoting pin under action of the actuator of the pickup unit inorder to move the cam into a position in which the cam is enabled tocome into engagement with the engagement member of the secondtransmission member; and wherein the second transmission member includesa gear wheel.
 2. The disk drive unit according to claim 1, wherein theengagement member of the second transmission member includes aprotrusion provided on the second transmission member in a position suchthat the protrusion is enabled to come into engagement with theengagement member of the pickup unit.
 3. The disk drive unit accordingto claim 1, wherein the first transmission member is a gear rack whichis positioned such that the gear rack is in engagement with the gearwheel when the pickup unit is in the read and/or write position, andsuch that the gear rack is out of engagement with the gear wheel whenthe pickup unit is in the home position.
 4. The disk drive unitaccording to claim 1, wherein the engagement of the engagement membersof the pickup unit and the second transmission member is caused by amovement of the second transmission member and the simultaneous movementof the engagement member of the pickup unit into the position where theengagement member is enabled to come into engagement with the engagementmember of the second transmission member.
 5. The disk drive unitaccording to claim 1, further comprising a control unit that isprogrammed such that the drive of the second transmission memberconsists of a sequence of stepped driving movements, which sequence isstopped when the first and the second transmission member are inengagement, or when a preset amount of driving movements is reached. 6.The disk drive unit according to claim 1, wherein the secondtransmission member is operatively connected to a motor for driving thesecond transmission member.
 7. A device for reading and/or writinginformation from/on an optical disk, provided with the disk drive unitas claimed in claim
 1. 8. A disk drive unit for a disk comprising: aslide of a slide mechanism; a pickup unit mounted to the slide whereinthe slide mechanism is adapted to move the pickup unit along the diskbetween a home position and a read and/or write position, the slidemechanism comprising: a driven first transmission member which isoperatively connected to the slide for moving the slide; and a drivingsecond transmission member which is only in engagement with the firsttransmission member when the pickup unit is in the read and/or writeposition, wherein the pickup unit and the second transmission membercomprise engagement members which are adapted to come into engagement atleast when the second transmission member is not in engagement with thefirst transmission member so as to move the pickup unit away from thehome position, wherein the movement causes the first and secondtransmission members to engage, wherein the engagement of the first andthe second transmission member is detected by a detecting member.
 9. Thedisk drive unit according to claim 8, wherein the detecting member isformed by the pickup unit.
 10. The disk drive unit according to claim 9,the further comprising a control unit that is programmed such that thedriving movement of the second transmission member is stopped when thepickup unit detects the engagement of the first and the secondtransmission member by detecting a surface of a disk which is placed inthe disk drive unit.